Electrical and Thermal Transport Properties of the β-Pyrochlore Oxide CsW₂O₆

Abstract

We report the electrical resistivity, thermoelectric power, and thermal conductivity of singlecrystalline and sintered samples of the 5d pyrochlore oxide CsW2O6. The electrical resistivity of the single crystal is 3 m cm at 295 K and gradually increases with decreasing temperature above 215 K (Phase I). The thermoelectric power of the single-crystalline and sintered samples shows a constant value of approximately −60 V K −1 in Phase I. These results reflect that the electron conduction by W 5d electrons in Phase I is incoherent and in the hopping regime, although a band gap does not open at the Fermi level. The thermal conductivity in Phase I of both samples is considerably low, which might be due to the rattling of Cs + ions. In Phase II below 215 K, the electrical resistivity and the absolute value of thermoelectric power of both samples strongly increase with decreasing temperature, corresponding to a transition to a semiconducting state with a band gap open at the Fermi level, while the thermal conductivity in Phase II is smaller than that in Phase I.

Single-Crystal Growth of Layered Birnessite-Type Manganese Oxides and Their Delamination into MnO2 Nanosheets

“…Therefore, it is necessary to reduce the grain boundaries to evaluate the intrinsic physical properties of the materials. The reduction in grain boundaries is achieved through grain growth, hot pressing, spark plasma sintering, and the addition of sintering additives. − Tiling nanosheets tightly onto a substrate is a promising approach for applying nanosheets to sensors and electrodes. The interface between the two nanosheets is expected to strongly influence the physical properties, similar to grain boundaries in the bulk substance.…”